[7/15] feat(git): add `Branch::rename` method

[arxanas]

Stack:

• https://github.com/arxanas/git-branchless/pull/1220
• https://github.com/arxanas/git-branchless/pull/1221
• https://github.com/arxanas/git-branchless/pull/1222
• https://github.com/arxanas/git-branchless/pull/1223
• https://github.com/arxanas/git-branchless/pull/1224
• https://github.com/arxanas/git-branchless/pull/1225
• https://github.com/arxanas/git-branchless/pull/1226
• https://github.com/arxanas/git-branchless/pull/1227
• https://github.com/arxanas/git-branchless/pull/1228
• https://github.com/arxanas/git-branchless/pull/1229
• https://github.com/arxanas/git-branchless/pull/1184
• https://github.com/arxanas/git-branchless/pull/1230
• https://github.com/arxanas/git-branchless/pull/1231
• https://github.com/arxanas/git-branchless/pull/1232
• https://github.com/arxanas/git-branchless/pull/1233

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feat(git): add Branch::rename method

Not used now, but might be used in the future to generate local-friendly branch names for the Github forge.